pendolino trains

[boxer]

According to the Virgin ad, these trains return energy to the national grid when breaking, how?

[dundurn]

It's the same principle as when you brake a car. If you depress the clutch it takes a lot more braking force to stop the car than if you leave the clutch alone and take your foot off the accelerator. Because the engine is still turning but is not under power it effectively creates a drag force on the wheels. In the case of the train they can go one better. Because the motor is electric it can work as a generator when the train is slowing down and pump power back into the overhead lines.

Some cars and several bus designs have used analogous systems either spinning up a flywheel to save the energy gained in braking or compressing a volume of air. When accelerating away again, power is taken out of the regenerative braking system before demanding more fuel.

[boxer]

Thank you, dundurn

[8733mags]

The modern electric locomotive has the ability to generate electricity as part of its braking action. This electricity can be fed back up to the pantograph on top of the loco and taken back to the supply. This action is called regenerative braking and both AC and DC motors can perform this feature. It has taken many years for the control circuitry of the motors in the trains to be able to handle the power levels involved in slowing a long train from high speed.

[boxer]

Thank you also, 8733mags